The present invention relates generally to devices that monitor the condition within an ear, and more specifically to devices that are external to the ear and monitor the condition within the ear using a probe placed within the ear canal. Even more specifically, the present invention relates to a hearing tester which emits test signals into the ear through a probe placed within the ear canal, and then uses the distortion-product otoacoustic emissions (DPOAE) from the ear to determine middle-ear function.
Devices that monitor the condition within an ear use a probe placed within the ear canal. The probe is placed within the ear canal by the person performing the test (the "operator"). For example, in DPOAE testing, all existing equipment uses a probe which seals into the ear canal. The probe is either attached to the device through a cable or, as illustrated in patent application Ser. No. 08/832,277, the probe is integrated into a hand-held device. In addition, existing devices display the results of the test on a screen while the test is being performed. The screen is external to the device.
One problem with existing devices is their susceptibility to extraneous noise introduced into the ear canal or measurement system. For example, in DPOAE testing, the otoacoustic emissions produced by a healthy ear are extremely small in magnitude. The emissions typically range from -10 dB SPL (Sound Pressure Level) to +20 dB SPL. Any kind of extraneous noise introduced into the ear canal or measurement system can mask these emissions and give a false negative response.
Sources of extraneous noise are external noise from the environment and biological noise from within the person whose ear is being tested. Environmental noise arises from improper positioning of the test probe within the ear canal, thus allowing noise to enter the ear canal from the sides of the test probe. Biological noise arises from teeth grinding, sneezing, etc. on the part of the person whose ear is being tested.
Thus, when using existing devices, there is a need to determine if extraneous noise is present, to determine the source of the noise, and to eliminate the noise before and during a test. For example, when using the hand-held device of patent application Ser. No. 08/832,277, there is a need to know if environmental noise is present so that the operator can eliminate the environmental noise by repositioning the hand-held device against the patient's ear and applying the appropriate amount of pressure to maintain a seal between the test probe and the entrance to the ear canal.
Another problem with existing devices is the use of an external display. The operator monitors the progress of the test while the test is being performed by viewing the display. Simultaneously performing the test and monitoring the display can be awkward, especially when the operator is concentrating on the proper placement of the test probe within the ear canal. For example, in the hand-held device illustrated in patent application Ser. No. 08/832,277, holding the device so that the test probe is properly positioned within the ear, and simultaneously viewing the display can be difficult. Thus, a need exists for using the device without the necessity of monitoring the display, or in other words, "eyes-free" operation.